Telephone system



Sept. 23, 1941. F. SIMON TELEPHONE -SYSTEM F'i led March 1, 1939 2Sheets-Sheet 1- INVENTORi FRANZ SIMON ATTORNEY Sept. 23, 1941. F. SIMOANTELEPHONE SYSTEM 2 Sheet-Sheet 2 Filed March 1 INVENTOR: F RAN Z SIMONATTORNEY.

Patented Sept. 23, 1941 2,25t,872 TELEPHONE SYSTEM Application March 1,1939, Serial No. 259,163 In Germany March 11, 1938 7 Claims.

Often a series of special switching operations in the selector and theinitiating of switching operations at other points of the connectingpath are carried out by control devices for final selectors in automatictelephon systems which bring about the necessary switching operationsfor setting up and maintaining the connection between two subscriberslines. The special control operations can be carried out in acomparatively simple manner by means of selectors which are providedwith an auxiliary switch mechanism serving as a control switch. In thefinal selectors without control switches however the use of a more orless large number of auxiliary relays is necessary in order to carry outthe particular control operations. The influence of the cost of theseauxiliary relays and the economic running of the system can perhaps beleft out of consideration as it istrivial. This, however, is notpossible with reference to the complications in the circuit caused bythe introduction of the auxiliary relays and the consequent difiicultiesin maintenance and testing of the installations. It is further obviousthat the base plates of the set of relays can only take a certain numberof relays so that often the necessary connection of the specialauxiliary relays makes it necessary to use base plates of largerdimensions. As a rule this results in larger selector frames and alarger space is required for the whole installation.

The present arrangement relates to final selectors without controlswitches to which in addition to individual lines (subscribers lines)lines directed to the groups, e. g. junction lines to other exchangesand to operators positions, are connected and in which a selectedconnecting set can perform switching operations at points of theconnecting path and the line which leads to the final selector. Theobject of the present invention is to make possible the preparing of allthe necessary control operations for the various connection with thesmallest possible number of relays in the final selector.

In order to obtain this result one winding of those differential relayswhich bring about switching operations in the connecting path, when theconnection and an earth connection to a called set exists, is under thecontrol of a testing device during the testing operation in the settingup of the connection and when a selected setting" line is engaged, aswell as when the whole direction lines of the group are engaged, bringsinto effect an engaged signal as this relay is preof an opposite windingduring the selection of a free line of a selected group.

In the drawings comprising Figures 1 and 2 a local telephone exchange isshown in which local, incoming and enquiry connections extend over thesame final selector without control switches, to which, in addition tothe individual line, groups of directed lines are connected.

It is understood that the invention is not limited to local exchangesbut can be used in other installations in which individual lines andmultiple connected lines can be reached over final selectors and thefeeding bridge of the called subscriber is provided with a difierentialrelay which on the connection of. potential to the subscribers setbrings about switching operations at any desired points of the existingconnecting path.

The drawings do not show all circuit details of the connecting devicesand the connecting'path but only those which are necessary in order thatthe control operations bringing about the switchin'g throuig'h of thevarious relays connected according to the invention should be clearlyunderstood.

I. LOCAL CONNECT'IdN BETWEEN SUBSCRIBERS TNl AND TNZ known switchingoperations. The group selector,

GW is set by thefirst impulse train on the bank over which the finalselectors are reached to which contact' bank the junction line of therequired subscriber TM is connected. When the wipers l, 8 and 9 reachthe connection of a free final selector LW the following test andseizing circuit is completed: test relay not shown in the group'selectorGW, wiper 9, contacts H], Hal, l2lc'lw', relay Al, winding III, In thegroup selector there follows in known manner the stopping of theoperation, the switching throughof the talking conductors, thedisconnection of the impulse bridge and the locking of the seized finalselector.

r The relay Al in thefinal selectorLW operates in the seizing circuit.At contact Hal it opens vented from o erating by the local connectionthe's'hort circuit for may CI and it also opens the contact l3a in thecircuit for the driving magnet 0f th filial selector,

The relay CI operates. At contact l icl it prepares the testing circuitand at contact I5cI the circuit of the vertical magnet H. At contactI6cI the relay CI locks up independently of the off-normal contactI2lclw. Further it closes its contacts I'lcI, IScI, for a purpose to beindicated later and opens contact I9cI. Winding III of the relay AI isshort-circuited at contact IBcI. The impulse and feeding bridge relay AIis not restored, however since its windings I and II are connected inthe microphone feedingcircuit of the subscriber's line Tnl,

When the calling subscriber sends out the impulse train for setting thefinal selector in a numerical impulse bank the impulses are transmittedto the vertical magnet H over contact I3aI: contacts 20122, 2IpI,winding I of relay VI, contacts I5cl, I3al, 22ul, 23wlw, vertical magnetH,

In this circuit the relay VI also operates and opens its contact 2401and at contact 251)! short circuits its winding II so that it does notrestore between the individual impulses. On the first vertical step ofthe final selector the contact I2klw is opened and hence the winding IIIof the relay AI is disconnected from the seizing circuit. The contact26km is closed and hence the switching over from vertical magnet H tothe rotary magnet D is prepared.

After th coming into effect of the impulse train the relay AI remainsenergized for a long period. The contact I3al remains open. The relay VIrestores. The relay UI is energized over: contacts 29122, 2IpI, 24M,ZSkZw, IIcl,

winding I of relay UI, rotary off-normal contact 23wlw, vertical magnetH, The Vertical magnet H cannot operate in this circuit in view of thehigh resistance winding I of relay UI. At contact 22uI the verticalmagnet of the impulse contact I3aI is disconnected and this is broughtin connection with the rotary magnet D over the contact 212. The contact23m is opened and hence premature connection of the rotary magnet D in acircuit bringing about the automatic movement of the selector isprevented. At contact 29uI a holding circuit is prepared over thewinding 11 of the relay UI which is necessary for the further selectivesetting of the final selector. The contact 3IluI serves to prepare thetest circuit. By the opening of contact 3IuI a premature connection ofwinding II of relay BI is prevented.

The opening of contact 32uI and closing of contact 33uI serves toprepare the first call. The opening of contact 34uI in the circuit ofwinding III of the relay BI has a purpose to be indicated later, notcoming into consideration with the present connection.

The second impulse train serving to set the final selector on thjunction of the numerical impulse receiver is transmitted to a rotarymagnet D by means of the contact I3al. In series with the rotary magnetD the control relay VI operates and at contact'35vl closes the holdingcircuit of winding II of relay UI so that this relay remains energizedafter the opening of contact 23wlw on the first rotary step andinterruption of the circuit over the winding I. The opening of contact351M prevents the testing operation during the rotary movement of thefinal selector.

At the end of the rotary impulse train the relay VI restores. 35M. Theholding circuit over winding II of relay UI is interrupted at contact35M. During The test circuit is closed at contact switches through thetalking conductors.

the release period of the relay Ul the condition of the selectedjunction line (free or engaged) is determined.

Should the line be free then in View of the high resistance of thecut-off relay T2 associated with the junction line only the test relayPI of the series test relays PI and P2 operates: contacts Mcl, 301M,361M, winding I and II of relay PI, relay P2, wiper 31, contact 38,relay T2,

The relay PI locks the selected junction line by short-circuiting itshigh resistance winding I at contact 39pl. It opens the contact ZIpI,closes the contacts 4Ilpl and 4Ipl in the feeding bridge, prepares atcontact 42pl the energizing circuit for the relay ZI coming into effectafter the reply of the selected subscriber and at contact 43pl closes acircuit for winding III of the relay VI contacts 43pl, Mel, Winding IIIof relay VI, contact 33ul,

The relay VI is energized so long as the slow relay UI holds itsarmature attracted after the free testing of its armature. At contacts45M and 46m it short circuits the winding II of relays Y! and BI and atcontact 41b! disconnects the winding I of relay BI and at contact 48mconnects the calling current source. The calling current flows over thefollowing path: calling current, contacts 481M, liilpl, winding I ofrelay YI, contact 49102, wiper 50, contact 5|, subscribers station T122,contact 52, wiper 53, contacts 45'vI,'4IpI, 462M, 54132,

After the release of relay UI the winding III of the relay VI is broughtunder the control of a time switch not shown by the opening of contact33a! and closing of contact 32uI and is connected at particularintervals e. g. every 5 seconds. The relay VI is energized.

After the selected subscriber replies in a call pause the relay YIoperates but not the diiTerential relay BI which is also in the feedingbridge. The contact 55yI is opened. At contact 56yI the switchingthrough relay ZI is connected and at contact 5'I2I locks up in a circuitindependent of contact 56yl and at contacts 58zl and 59z| The contactMel in the circuit for winding III of relay VI is opened and in this wayinfluences the winding of the control switch.

The two subscribers TnI and Tn2 are connected with one another. When atthe end of conversation the calling subscriber hangs up his receiver therelay CI is short circuited at contact IIaI. It restores, however, andat contact I4cI opens th circuit of the relays PI and T2. The feedingcircuit for the subscriber TM is interrupted at contacts IIlpI and iIpI.The final selector LWI is brought to its normal position. This is donein such a manner that in the first place the rotary magnet D of thefinal selector energizes over: contacts 20p2, ZIpI, 241M, ifilclw, I9cI,281d, rotary magnet D, Over the contact 69d the winding II of relay UIoperatesvand opens the circuit of the rotary magnet D at contact 281.This magnet restores. The alternate play between the rotary magnet D andth relay UI is repeated until the wipers of the contact bank havedropped down to their lowest position. The rotary off-normal contact26lclw is then opened so that the rotary magnet D cannot take up anyfurther impulses. The final selector then reaches its normal position.

The release of the relay CI brings about the release of the precedingselector since it is dis- Ebhnected froin the incoming seizingconductors hythe opening of contact IBcl.

whn the junction line of the selected subscriber Tn2 is engagedwhen thefinal selector sets on it the relay Pl cannot operate. This has theresult that after the release of the control relay U! also determiningthe test period, a circuit is completed over winding II of relay Bl;-i-, contact 54122, winding II of relay Bl, resistance 6!, contacts3l'ul, BZwZw, 6312!, The relay 3! by closing the contact 641)! connectsthe engaged signal to the winding III of the relay Al. The callingsubscriber hears the engaged signal and hangs up. g V The reversal ofthe direction of feeding current for the calling subscriber occurring onthe opening of contacts B5bl and 66bl and closing of contacts Bibi and68bl is not important for the present connection.

II. C'Ofiii'EbTION Ovna A LINE on A GROUP or LINES IN THE SAMEDIaEo'rIoN Groups of direction lines are connected to the finalselector; it is assumed that there are two groups of which the two linesVLI I, VLIZ, VLZI are engaged. After the setting of the final selectarcorresponding to the characterizing digit of the required group theselector is automatically set on the first free line independently ofwhich group has been selected. The further switching operations in thefinal selector depend upon whether the line groupVLl I, VLIZ, Or theline group VLZI, VL22 has been selected.

While the further setting up of the connection is carried through in thesame manner as in the selection of an individual line by the setting orthe final selector on a free line of the groups VLIl, VLI2, a switchingoperation takes place in the final selector on the seizing of the freeline of the groups VL2I, VL22 by which all sections connected with thetalking conductors are disconnected. A continuous metallic connection isset up between the contacts of the group selectors and the wipers of thefinal selectors.

1. Connections with a junction Zine of group VLII, VLIZ After theselection of that bank in which the junction lines VLl'l, VLiZ areincluded or after the setting of the wiper in the final selector on thecontact of the first junction line VLl l, the general contact Task isclosed.

If the junction line VLII is free then in the same way as described insection I the test relay PI is effective after the release of relay Viand initiates the completion of the connection.

If the junction line VLH is engaged the relay Pl cannot operate. Afterthe release of the control relay Ul determining the test period, theengaged signal must not be connected yet however, in contrast to thecase of a connection with a guarded individual line, since the engagedcondition of the other lines of the groups must first be determined. Forthis purpose after the re lease of relay Ui over contact 'His'lc awinding III of relay BI is connected: winding III of relay Bl, contacts351, Task, ZGkZw, 2411!, Zlpi, 20472, 1-. At the same time overcontact'3 lul the circuit over winding II of relay BI is also c'ompletedfcontacts 6311!, EZwZw, 3lul, resistance 6|, winding II of relay Bl,contact 54102; -i-. The winding III is an opposite windmgto the windingII. The effects of th current new:

ingtnrcu n both the windings cancel oiit. ,The relay BI does notoperate. 1 v

The rotary magnet D is connected: rotary magnet D, contacts 28ul, l0sic, 26klw, 24M, 2lpl, ZQpZ, The rotary magnet D connects the winding IIof relay Ul at contact 6 0d which interrupts the circuitoi the rotarymagnet D. The alternate connection and disconnection of D and UIcontinues until the test wiper 31 reachesthe test contact of thejunction ,line VLIE. The relay Pi operates in the test circuit extendingover contact H and the cut-off relay T!2-. In the same way as withtheconnection to a single line, since the cut-off relay TI2 has a highresistance, the test relay P2 does not operate in the present connectionalso. At contact 2lpi the circuit for the rotary magnet D and thewinding III of the relay BI is interrupted. At contact 63p! the circuitover the winding II of relay BI is opened.

The further setting up of the connection takes place in the same way asdescribed in Section I.

If all junctionlines of the group VLI l,'VL|2 are engaged the finalselector is stepped onto the contact set of the last junction line sincethen the general contact Risk is open. The rotary magnet is no longerenergized. The circuit of winding III of relay BI is interrupted. RelayBl operates over its winding II and connects the engaged signal as inSection I.

2. Connection with a junction ,zme of groups VL21, VL22 The cut-ohrelays T21, T22 and the junction lines VLZE, VLZZ have a lowerresistance than the cut-off relays Tl, T2, TH, 'IIZ of the reniaininglines connected with the final selector. or. the setting of a finalselector on the junction line VLiEl, VL22 the test relay P2 alsooperates therefore. In known manner, it disconnects in the finalselector all devices which are in connection with the talking conductorsand cornpletes a "continuous metallic connection between the incomingtalking conductors and the wipers 56 and 53 of the final selector. Bythe opening of contacts E3102 and Mp4 there follows thedisconnection ofthe bridge relay AI, by the'opening of contact 49 02 the disconnectionof winding I of relay Yl from the wiper 53, by the opening of contactMp2 the diseonnection'of the positive poleof the winding II of relaysB-land Yl and by the closing of contacts 15122 and T6102 the directmetallic connection of the conductors outgoing from the contacts of thegroup selector with the wipers 50 and 53 of the final selector. In thesame way as with connections to 'a junction line of groups VLII, VLIZ,in connection with the junction lines VLZI, VL22 also, afer the settingof the selector on the first junction line VLZE, when the same isengaged on energizing of the relay Bl for the purpose of transmittingthe engaged signal is prevented. Over the general contacts lflsk andcontacts corresponding to these, the reverse winding III of the relayEllis connected. When the free junction line VL22 is reached the testrelays PI and P2 are energized and open the circuit of the rotary magnetD at the contacts 20122, Zipl, and the winding III of relay Bl as wellas the circuit for winding II of relay BI at the contacts 6315i and Mp2.f-When all the groups VLZI, VL22 are engaged and the selector reachesthe contactset of the final selector of the group, the contact Itsk or acontact correspohcihgto this is open. -Triewind= ing III of the relay BIis disconnected. The relay BI then operates due to current'flowing overits the junction line of a calling subscriber Tnl and transmission of acharacterizing digit for exchange connections, the group selector GWsets on the free exchange line VLa. In the test circuit over the wiper9, the contact 80 and the conductor 8| the relay 02 operates and closesa circuit over the relay C3 and the winding I of the relay X2 at contactH1002. The relay X2 by opening the contact IBIrZ prevents the energizingof the relay XI over its winding III after the closing of the contactI02c3. The call relay A2 is connected and at contact I04c2 the uppertalking conductor of the exchange line VLa is switched through. Inbridge to the access means, reached over the group selector GW, to thetalking conductors of the exchange line VLa are the relays SI and XI.The relay XIv is adifferential relay and it is not operated in themicrophone feeding circuit. The relay SI only is energized. Among otherthings it closes the contact I05sl in the exchange line.

The relay C3 connected by relay C2 in the seizing operation connects thewinding I of relay L over its contact H3603, which contact IITIZconnects th winding II of relay X2 in parallel to the condenser I08,which however is not im ortant for the moment.

Between the conductors H and III of the exchange line VLa the followingdirect current bridge exists: conductor I I0, contacts I I Iasl, IsI,I04c2, H222, repeater winding H3, contact I46x2, winding II of relay L,repeater winding. I I4, contacts H522, IIBasI, conductor II'I. By meansof this rectifying bridge the call impulse is transmitted in the knownmanner to the remote exchange and controls the call device therein.

Over the winding II of relay L the current flows in such a directionthat it increases the efiect of the current over the locally connectedwinding I. The energized condition of relay L is therefore not effected.

The impulse train sent out from the calling subscriber for setting aselector in the remote exchange is transmitted fromthe bridge relay SIby means of the contact I05sl.

IV. SETTING UP OF AN ENQUIRY CoNNEcTIoN The enquiry connecting relaygroup which consists of the relays Z2 and Y2 is connected to relay C3 inpreparation by means of contact H803. The energizing and holdingcircuits of relay U2 and U4 which are operated on the switchingover andexchange connection'are prepared at contact H903.

For the purpose of setting up an enquiry connection the callingsubscriber TnI momentarily operates the enquiry key RTI at his apparatusand thereby connects earth to the talking conductor. The differentialrelay XI operates, and the feeding bridge relay SI remains energized. Atthe contact I2trl the circuit over the winding I of relay Z2 iscompleted: contacts II8c3, I2Iy2, winding I of relay Z2, contactsIZIJa'I, I22u4, I23u3, Relay Z2 closes the contact I24z2 so that itprepares to lock up over winding II and prepares an energizing circuitover the winding I of relay Y2. As long as the contact IZIJwI iscompleted the last mentioned two winding s are short circuited. Atcontact I25z2 the choke DH is connected in bridge between the conductorsH0 and H1 and the exchange line VLa. The contacts H222 and H522 areopened and contacts I2Be2 and I2I22 are closed. The part of the exchangepath connected with the exchange subscriber Tnl is disconnected therebyfrom the outgoingexchange line VLa and connected to the enquiry path RL.

By the release of the key RTI and disconnec tion of earth thediiferential relay XI restores again. The contact I20$I is opened. Theshort circuit of the winding I of Y2 and II of Z2 is removed. The relayY2 operates: contacts I I803, I2Iy2, windings I and II of relay Z2,winding I of relay Y2, contacts I24z2, I22u4, I23u3, The contact I 28y2is closed and thereupon the contact I 2 I112 is open. The followingholding circuit now exists'for relays YZ'and Z2: contacts 803, I28y2,winding II ofrelay Y2, winding II of relay Z2, winding I of relay Y2,contacts I24e2, I22u4, I23u3,

At contact I29y2, the energizing circuit for the relay U2 of the switchrelay group is further prepared. The relay U2 does not operate since therelay L is energized and the contact I301 is open.

At contact I 3Iy2 a conductor of the enquity path BL is switched throughso that now since the contact I32sl, is-also closed, the call relayconnected to the conductors 84 and 85 of the local network is operated.A free finder switch AS sets on the enquiry line. The enquiringsubscriber TnIsets the group selector GW and the final selector LW onthe subscriber required in the enquiry connection.

The circuit of the relay AI in the final selector exists as followsafter the seizing of the final selector and during the whole enquiryconnection: winding I of relay AI, contacts b1, 'I3p2, wiper I of GW, Iof AS, contact 83, conductor 84, contacts I33u4, I2622, repeater windingH3, contact I 46192, winding II of relay L, repeater winding H4, contactI2'Ie2, I3Iy2, I32sl, I34u4, conductor 85, contact 86, wiper 2 of AS, 8of GW, contacts Mp2, GGbI, winding II of relay Al,

In this circuit the current flows over the winding II of relay L in sucha direction that it does not remove the effect of the current flowingover the locally connected winding I. The relay L, therefore, remainsenergized.

The setting of the final selector takes place in the manner described inSection I.

V. TAKING OVER on THE EXCHANGE CoNNEcTIoN BY THE SUBSCRIBER TNZ In thefeeding circuit of a called subscriber Tn2 the windings I and II ofrelay YI are included and the windings I and II of the relay Bconnecting the engaged signal when a selected individual line is engagedor after the testing of the lines of a group which are all guarded; Thewindings I and II are connected differentially so that the relay BI isnot energized over the feeding circuit, The winding II is the samewinding as is connected when the relay must operate in order to give outthe engaged signal. 7

For the purpose of taking over the exchange connection in conjunctionwith the enquiry conversation with the subscriber TnI, the subscriberT112 must press momentarily the key RTZ on his apparatus. As a resultearth is connected to the lower talking conductor. The windings II ofrelays YI and BI are short circuited. The relay YI remains energizedover its winding I. Relay BI operates. The closing of contact 64bI iswithout efiect since the contact 55yI in series with it is open. Thecontacts 65b1, 66b| are opened and the contacts 61b1, 6.8 bl are closed.There follows a reversal of the direction of current flowing over theenquiry path since the winding I ct relay Al connected over negativepotential is transferred from the upper talking conductor to the lowerand the winding II connected with positive potential is transferred fromthe lower talking conductor to the upper. The result is that thedirection of current over the winding II of relay I, (Fig. 2 is changedso that the effect of; the current over winding II cancelled out that ofthe current over winding I.

The relay L restores and at contact I36} closes the energizing'circuitover winding I of relay UZH contacts H903, [30L [2.9112, |35u3, windingI oi relay U2 At contact B6102, an energizing circuit is prepared overthe winding I of relay U3 which however again operates so long as itswinding together with its winding II of relay U2 is short-circuited atcontact I 3BZ. By the opening of contact l3'lu2, l3 8'u2, and closing ofcon tacts l39u2 MEIuZ, the calling subscriber Tn! is disconnected fromthe exchange line VLc and this line is connected over the conductors 84and as of the enquiry pathl There is no effect on the current flowingover the enquiry path to the winding II of relay X -2 since the contactHill is open.

On the release of the key RT2 of the subscribers set T112 the relay Blsets back its contacts to their. norrnal positions shown in the drawingsthereby altering the direction of the current over the enquiry pathagain and over the winding II of relay. L. The windings I and II acttogether so that the relay L operates, the contact Hill is closed andthe contact Hill is opened.

At contact Hill the winding II of relay X2 is conipleted. The currentflowing over its winding has a direction that it increases the effectover the locally connected winding II The relay X2 thereforeremainsenergized.

At contact 1301 the short circuit for the Winding II of the relay UZ andI of relay 13 is removed. The relay U3 operates, disconnects thewinding I of relay U2 at contact 135143, connects the windin of'relay USat contact Hut and a slowto operate relay U4 at contactlgaii. By theopening of ccnt'act' 12311;, the holding circuit overthe relays Y2 andZ2 is opened and at contact H316 a later energizing of this relay isprepared. The release of relay Y2 and Z2 results in the openingcfcontact 131312- in the enquiry path and of contact |23y2 in theenergizing circuit oi the winding Iof relay Ut The disconnection of theenquiry line RL'froxn the exchange line VLa resultsfrcrntheopening ofccntacts H522, l2la2 and the switching through of the exchange linetakes place t contacts 1 1122 and H522. e. choke 'DTI disconnected bythe opening of contact [2522.

criber T112 taking over the connection e sub is now connect ed overthe'final selector, group sel ct orfand conducmr c4 and 85 with the lefta d wnding of the repeater Ue to the exchange lirfeV L'a This switchingover of the exchange connection to the exchange line is performed bytherel ayBl arranged on the other set of the connecting path at thefinal selector and this re: lay transmits the transferring impulse sentout the subscriber by reversingthe current direction in the enquirypath. The relay Bl is that riiay which when an individual line isengaged 9? a l. i e f a'sele sd e eubere e age 9 1 e t s a enga e s g Onits operation relay U4 opens the contact l22u4 and at contgict lflllrmfinally prepares the energizing circuit over the winding I of therelay Z2. By the opening of contacts [331.54 134m and the closing of thecontacts I 451:4; 146w! the en: quiry switching over point and the.enquiry line EL extending through the local exchange are connected bymeans of the contacts l 3,' lu2 and 138112 of the part of'the exchangeconnecting path from the present exchange connection in order that overthis part of the exchange connection an enquiry connection caneventually be set up again.

VI. SETTING AN Enquiry CONNECTION on THE PART or THE Sunscnmna TN2manner reverses the direction of the currentiiowing over the conductors84 and 85. This current reversal operates on relay X2 in such a mannerthat current now flows over the winding II in the opposite direction tothat flowing over the winding I. Relay X2 restores and at contact lil lrz connects the winding III of the relay Xl:+,

winding III of relay XI, contacts llll'x2, 10203, IQOcZ, Relay XIoperates and contact I ZUmI closes the energizingcircuit alreadydescribed over winding I of relay Z2. l

The relay Z2operatcs. On the release of the key RTZ and release or therelay Bl the direction of current over the conductors Bland is againreversed. The relay X2 operatesaga'in. The relay XI restores ThereIa'yYZ operates. The enquiry switching operation is now'performedunder the control of the final selector and also the engaged signal isconnected b'y. the relay Bl serving to lock the selected'linef Thesubscriber can setup the enquiry connecting path.

VII. TAKING OVER THE ENQUIRY CONNECTION BY THE SUBSCRIBER CALLED IN THEENQUIRY CONNECTION If the subscriber called in this enquiry connectionwishes to take over the exchange connection again he operates hisenquiry key since the subscriber was selected in the same manner as thesubscriber Tn2 over a final selector. The

carried out by the short circuiting of winding I of relay U3 at contactISEJZ and of winding II of relay U2. Relay U2 restores. The contactsl36u2, 5391.42, and M0142 are opened and the contacts 131102 and I 38u2are closed. The enquiring subscriber Tn 2 is disconnected. Relay U3stillremains energized over its winding II and maintains the relay U4connected as a result at'contact i42u3. 'Ihe'alt'erations of the currentdirection occurring during the presence of the key do not affect thewinding II of relay X2, since the contact mu is open. After the releaseof the key at the call subscribers set the relay 3 at the final selectoris operated. Relay L operates and at contact I332 VIII. INCOMINGEXCHANGE CONNECTION In a call over the exchange line VLa the call relayA2 is energized by means of the call current connected to the callingexchange. It connects the holding relay I-IrI contacts I5Ilc2,I5Ia2,'relay Hrl, contacts I523], I53asl, The relay HrI locks up atcontact I 54ml independently of contact I5I a2 and at contact I55hrIcloses the circuit of the call lamp ALI associated with the exchangelamp VLa.

The operator takes upher instrument whereby the contact I 557m is closedShe operates the enquiry switch ATI of the exchange line VLa and therebyenergizes the connecting relay ASI over the contact I56. The relay ASIprepares a holding circuit for itselfat contact I5'Iasi and opens thecontacts IIIasI, IIBasI and by closing the contacts I58asI and I59asIconnects the talking ap aratus of the operator in bridge between theconductors HE and III of the exchange line VLa. By the opening of thecontacts I 'MasI, I'I5asI and closing of the contacts IIIlasI, IGSasIthe relay Dr3 is bridged across the conductors I16 and IT! with itswinding II and III. Since the local line and the local network isbridged in the same way as the subscriber's line the call relayassociated with the exchange line of the local network operates andbrings about the setting of a finder switch on this line. The relay Dr3is energized in the circuit extending over its winding II and III andthecircuit overritslamp BLI at contact I80d r3 is opened.

The operator makes. an enquiry and finds the requirement of the callingsubscriber. Thereupon she-restores the enquiry switch to its normalposition. The relay ASI remains'energized over its contact I5lasl andthe contact I60 of the enquiry switch A'I'I. The connecting key VT isnow depressed momentarily and the relay V4 energizes: contacts I55hu,I68, I6I, relay V4, The relay V4 locks up at contact I62v4 independentlyof contact IISI of the connecting key VT. By closing the contactIii-3124 it connects the choke Dr2 in bridge across the branch of theexchange line VLa. By the opening of the contact Ifi lv the choke D74 isdisconnected. The talking apparatus of the operator is disconnectedtogether with the impulse contact 1182' by the opening of contactsI65v4, IBSM and the closing of contacts I6'Iv4, 58114 from the exchangeline VLa leading to the remote exchange and connected to that branch ofthe exchange connecting path which is connected with the local networkover the contacts l69asI and I'Hlasl. There follows further by theopening of contacts I'II2J4 and closing of contacts H2114 a switchingover of the relay Dr3 and by the connection of the impulse contacts nsithe setting up of an impulse circuit for setting the selector of thelocal network. At contact H8124 the winding I of relay Dr3 isdisconnected.

When the operator operates her dial switch in order to set the selectorin its home position the it reverses the direction in the circuit overthe",

scriber TM is engaged or if all junction lines VLI I, VLI2 and VL2I,VL22 in the required traffic' device are guarded then as described inSection I and IIafter the selection of the subscriber lines or after thetesting of all the junction line of the selected group the relay BI inthe final selector is energized by the closing of a circuit over itswinding II. By the opening of the contacts, fi 5bl GIibI and the closingof the contacts 6'IbI, G BbI windings II and III of relay D73. Theefiect o f the current over these windings now opposes the' current overwinding I. The relay Dr3 restores and at its contact I8Ildr3 connectsthe busy lamp BLI, so that the operator has a visible indication 2} thatthe selected subscriber as all the lines of the selected group areengaged. At the same time there follows in the final selector aconnection of the engaged buzzer to winding III of the relay Al I sothat the operatoralso receives the audible indication as well as thevisible one.

The relay BI associated with the final selector always carries out thesameswitching over on the coming into effect of an impulse transmittedfrom a junction point for initiating an enquiry switchingover or toswitch over .an exchange connec-' tion and also to register the engagedcondition of: the selected line. It always reverses the direction of thecurrent leading to the final selector. This current reversal alwayseffects the transmission to the exchange line andthereby in de pendenceupon its conditionefiects eitherfthe switching over required by thejunction line or the connectionof a visible engaged signal. Whatisclaimed is: 1

1. In a telephone system, three lines, an aut omatic switch havingaccess to one of said. lines, means for operating said switch tosaid oneline at different times to extend connections thereto from a second ofsaid lines, means in said switch efiective during the extension of suchconnec-. tions to test said one line and complete the connectionsthereto only if said line is idle, a busy relay controlled by said lastmeans and operated thereby whenever the line tests busy to transmit abusy signal, means for operating said relay at times over said one lineafter a connection has been completed thereto from said second line overthe switch, another switch having access to the third of said lines,means controlled by said relay upon said operation thereof over saidfirst line to hold the connection from said second line and seize saidother switch, and means for then operating said other switch over saidfirst line to extend a connection to said third line while theconnection from said second line is maintained.

2. A telephone system as claimed in claiml, wherein said first automaticswitch and said other switch are identical.

3. In a telephone system; three lines; means operated to complete aconnection between two of said lines; means thereafter controlled by asubscribed over the first of said two lines for extending an enquiryconnection to the third line while holding the connection to the secondof said two lines; said last means including an automatic switch havingaccess to said third line, means controlled over said first line tooperate said switch to prepare the enquiry connection to said thirdline, means in said switch for then testing said third line, a relayoperated by said last means if said third line is busy to cause a busysignal to be transmitted over said first line, and means in said switchoperated to complete the enquiry connection to said third line if sametests idle; subscriber controlled means for thereafter operating saidrelay over said third line; and means controlled by said relay upon suchoperation thereof for transferring the enquiry connection to saidconnection to said second line, thereby to interconnect said second lineand said third line for conversation.

4. A telephone system as claimed in claim 3, wherein said first meansincludes an automatic switch identical to said switch having access tosaid third line.

5. In a telephone system, a rotary connector switch having access toindividual lines and groups of lines, means for seizing said switch andoperating it either to an individual line or to a group of lines, meansfor testing an individual line if said switch is operated thereto, saidlast means efi'ective also to test the lines of a group successively ifthe switch is operated to that group, a relay having a pair of opposingwindings, one of said windings being controlled by said testing meansand energized if the tested line is busy, means for energizing the otherof said windings only during the testing of group lines thereby toprevent the operation of said relay over said one winding whenever aline in the tested group tests busy, said relay operating over said onewinding when an individual line tests busy or after all of the lines ofa group have been tested and found busy, and means controlled by saidrelay upon such operation thereof for transmitting a busy signal,

6. In a telephone system, an automatic switch, lines accessible thereto,certain of said lines arranged in groups and others as individual lines,means for operating said switch to extend connections to said lines whenthey are called either in local, incoming or enquiry calls, a relay insaid switch operated to transmit a busy signal whenever said switch isoperated to a busy one ofsaid individual lines, said relay having meanseffective when said switch is operated to a group of said lines forpreventing said relay from operating while the switch is testing thelines of said group and for causing said relay to operate, thereby totransmit said signal, only when all of the lines in said group are foundbusy, and means for at times operating said relay over a called lineafter a call has been extended to that line by said switch thereby tohold said call and control the extension of another call from said liae.

'7. In a telephone system, an automatic switch, lines accessiblethereto, certain of said lines arranged in groups and others asindividual lines, means for operating said switch to extend connectionsto said lines when they are called either in local, incoming or enquirycalls, a relay in said switch operated to transmit a busy signalwhenever said switch is operated to a busy one of said individual lines,said relay having means effective when said switch is operated to agroup of said lines for preventing said relay from operating while theswitch is testing the lines of said group and for causing said relay tooperate, thereby to transmit said signal, only when all of the lines insaid group are found busy, and means for at times operating said relayover a called line after a call has been extended to that line by saidswitch thereby to control the transfer of said call to another line.

FRANZ SIMON.

